Which one of the following causes a frameshift mutation?

Point mutations that are frameshift mutations put the normal reading frame out of register by one base pair. The inseion of an extra base pair or the deletion of one or more base pairs falls into this category. Transitions and transversions are not frameshift mutations; they are substitutions of one base pair for another. Substitutions are the most common type of mutation. In transitions, a purine is replaced by a purine or a pyrimidine by a pyrimidine. In transversions, a purine is replaced by a pyrimidine or vice versa. It has been suggested that transitions occur spontaneously owing to the tautomeric changes in base- hydrogen-bond locations. Transversions can be caused by defective DNA polymerases. Ref: Weil P. (2011). Chapter 37. Protein Synthesis & the Genetic Code. In D.A. Bender, K.M. Botham, P.A. Weil, P.J. Kennelly, R.K. Murray, V.W. Rodwell (Eds),Harper's Illustrated Biochemistry, 29e.